Chord zither with tubular frame



June 2, 1970 J. R. ROHRBQUGH CHORD ZITHER WITH TUBULAR FRAME 3Sheets-Sheet 1 Filed Aug. 19, 1968 ,rwE/vme. Clo/{M J9. fla /260061,;

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J. R. ROHRBOUGH CHORD ZITHER WITH TUBULAR FRAME June 2, 1970 3Sheets-Sheet 2 Filed Aug. 19, 1968 4 jWE-MIbE. claw M J9. 30%?8006/4 J.R. ROHRBOUGH CHORD ZITHER WITH TUBULAR FRAME June 2, 1970 3 Sheets-Sheet5 Filed Aug. 19, 1968 United States Patent Int. Cl. Gd 1/12 US. Cl.84-286 10 Claims ABSTRACT OF THE DISCLOSURE A chord zither combining awooden sound box with a tubular metal frame, the strings being anchoredto and tensioned through the latter. In the preferred form, the chordbars are retained in an interchangeable magazine, which is slideablymovable over said strings within a bridge structure which may be mountedon said sound box, but must be supported (directly or indirectly) byadjacent parts of the metal frame. The upper part of said bridgestructure is a key table in which are mounted keys for operating thechord bars contained within the chord bar magazine, each chord bar beingslideable under the corresponding key to permit operation for allpositions of said magazine within the bridge structure.

This invention relates generally to chord zithers of the type in whichstring fingering is achieved by means of several bars movably mountedover the strings for selective damping of a particular set of stringswhen a corresponding bar is pressed by the player. More particularly,the present invention is a chord zither in which the sound box is ofuniquely light construction, but is enclosed within a metal outer framewhich absorbs the string tension and also provides the structuralstrength to support a bridge structure over the strings, in whichstructure several unique chord bar systems can be accommodated.

Chord zithers are widely used for instructional purposes in the publicschools. In addition, they have achieved wide spread popularity amongboth amateur and professional musicians because of the ease with which aplayer can learn to produce a wide range of enjoyable music.

The classical zither, known for centuries, is very diflficult to play,because of the manual fingering of the strings, and has been mastered byonly a relatively few expert musicians. In the chord zither, however, nostring fingering skill is required, since string fingering isaccomplished mechanically by the use of chord bars. These bars, verycommonly fifteen or sixteen in number, are resiliently supported abovethe strings and transversely to them. The underside of each bar isprovided with a number of felt damping pads; these are spaceddifferently for each of the chord bars. The top of each chord bar isprovided with a push button, or the like, suitably identified by letteror number, to inform the player of the chord to which that barcorresponds. Typically, the player holds the zither in his arms or on atable, strums the strings with a plecturum held in his right hand, andpresses down on selected chord bars with a timing in sequence clearlyindicated in sheet music written in terms of simple chord bar notation.Recognizable music can be produced within minutes, and a few hours ofpractice and study will enable the player to entertain others, and willteach him a great many musical fundamentals.

Despite its great popularity, the chord zither has heretofore beenhandicapped by certain mechanical and musical limitations, some of theselimitations having been inherited from the classical zither design, andsome of which have arisen out of the addition of chord bars, andassociated mechanisms. As will be explained hereinafter, the majormechanical and musical objection to the chord zither as presently knownare overcome by the novel and unique construction shown in the presentinvention.

The design of a zither inherently involves great mechanical stressbecause of string tension. Thus, in a typical first quality zither, suchas illustrated in the following specification, has 37 steel stringsextending for the length of the zither, and under high tension whentuned. The main body of the zither, upon which these strings aremounted, must be made very strong in order to resist the compression andbending stresses produced by so many highly tensioned strings.Unfortunately, the requirement of great structural strength to absorbthe great string tension forces is in direct conflict with the musicalrequirement of providing a sound box cavity of maximum size within thezither body. Moreover, zithers are made of wood, because only woodconstruction has been found to give the best acoustically resonantqualities for music production. There has been some use of plasticmaterials, and the application of the present invention includes soundbox construction of any suitable acoustically resonant material, even ifother than wood. However, throughout this specification, the sound boxis referred to as being of wood construction, since construction of azithers sound box out of other material is almost unknown up to thepresent.

The tuning system used in zithers presently known is generally of thetuning pin type. Each string is anchored to a small metal or wooden pinor peg which are set vertically into holes in the upper surface of thezither sound box, along one side of the zither. These tuning pins areheld only by friction, and tend to loosen because of age, or during use,or because of temperature changes, with the result that it is difiicultto keep the zither in tune.

Another objection to the tuning pins presenly used on zithers is thatthey clutter the top surface of the zither. They interfere with theplayers strumming hand in some positions of playing. Also, the zithersound box must be constructed with a massive block of wood along thetuning pin side of the zither, so as to provide a sound base for thosetuning pins. The tuning pin block thus required contributes very littleto the zithers resistance to string tension, and has the seriousdisadvantage that it further reduces the size of the sound box cavity.

In summary, zithers presently known are notoriously prone to get out oftune because of temperature or humidity changes, or merely some slightyielding of the sound box structure under the great force of the stringtension; and furthermore, the small size of sound box cavity in zithersheretofore known causes the tone of the instrument to be thin, weak inthe base notes, and unsatisfactory for playing to larger groups or inlarger rooms.

All presently knownchord bar mechanisms used in chord zithers have alsobeen characterized by certain defects and limitations, both mechanicaland acoustical.

From the mechanical standpoint, the outstanding defect or" presentlyknown chord zithers is that the chord bars frequently depart fromalignment, so that they do not produce the desired chord when operated.It is a universal experience of musical instrument retailers that achord zither which has been carefully made at the factory, carefullyinspected at the factory, and inspected when received by the retailer,will nevertheless be found out of adjustment after a few months instorage, or within a short time after being sold to the customer. Inspite of care by both manufacturer and retailer, presently known designslack the structural rigidity, and the reliable positive operation toassure that the chord bar mechanism, once inspected at the factory, willoperate reliably for years. Although the reasons why these difiicultiesare encountered with presently known zithers are not all clearlyunderstood, certainly one major cause of recurring maladjustment hasbeen the tendency of the chord bar structure to experience slightinternal movements, and also for a tendency for the strings to vary inelevation slightly, because of the lack of precision of tuning pins. Insome cases, one or more strings are moving slightly upward toward thechord bar, or slightly downward away from it; the player finds that hemust press very hard on one chord bar, but only very softly on another;moreover, he will find amazing differences in variations from oneinstrument to another, having the same model number and coming from thesame manufacturer.

From a music, or acoustic, standpoint, the outstanding objection topresently known chord bar zithers is their limitation to approximatelyfifteen chord bars. Different types of popular music, and differenttypes of classical music, require different sets of chords. In the past,chord bar zither manufacturers have simply manufactured differentzithers for each type of music. No attempt has been made to provide azither in which the chord mechanism could be shifted from one chordarrangement to another.

The foregoing are but a few of the most important objections to thechord zithers known up to the present time. The invention describedherein overcomes all of these objections, when all the novel featuresdisclosed are combined in the preferred form of the invention. However,in its simplest and most generic form, the chord zither of the presentinvention provides a zither which rarely has to be retuned, and whichproduces much richer and deeper tone than zithers known in the past. Thepresent zither employs a sound box of much lighter construction than themassive plank-like structures used in even small zithers of the past.The sound box is framed in a very strong but light frame, such as aframe of tubular steel, upon which the strings are mounted, and tuned,and which retains the strings at unchanging tension, regardless ofordinary changes in temperature and humidity, and regardless of moderatechanges in the sound box structure. The chord bar mechanism of thepresent invention relies upon the surrounding frame of tubular metal (orsome equivalent structure) to achieve a rigidity which keeps the chordbars in precise adjustment. Heretofore, it was believed that the chordbar mechanism required the same massive sound box structure as wasrequired for the string tension. In the present invention, however,greater rigidity is achieved despite the mounting of the chord barmechanism on a lighter sound box, since the points of mounting of thechord bar mechanism are located close enough to the tubular metal frameso that they are held in unchanging alignment.

In a preferred form of the present invention, the chord bars are housedin a magazine which may be shifted to any one of several positions abovethe strings, so that one set of fifteen chord bars, shiftable to twelvepositions, may provide as many as one hundred and eighty differentchords, instead of the fifteen usually found in a chord zither. Also,different chord bar magazines are readily interchangeable. In asimplified form of the invention, magazines of different chord bars maybe simply interchanged, without provision for shifting within the bridgestructure housing.

Interchangeability and shiftability of the magazine containing the chordbars, makes it impossible to rely upon the various kinds of chord baroperating buttons heretofore known. These have generally been mounteddirectly to the chord bar. In the forms of the present invention whichinvolved the use of a magazine, however, it is preferred to employoperating buttons which are movably mounted in the bridge structure,with the chord bars and their magazine freely slidable under said pushbuttons, or removable from them.

The foregoing and many other objects and advantages of the presentinvention will be understood from the following description of apreferred form of the novel chord zither. This preferred formincorporates many refinements, and it is to be understood that theinvention is not restricted to a design incorporating all thoserefinements,

4 but is intended to include all modifications and simplifications whichincorporate the basic novel features of relatively light sound box,enclosed within a strong and rigid outer frame, and supporting chordbars in a bridge structure which is anchored directly or indirectly tothe surrounding frame. The description should be read in connection withthe accompanying drawings, in which:

FIG. 1 is a perspective view of a chord zither constructed according tothe invention;

FIG. 2 is a plane view of the chord zither illustrated in FIG. 1;

FIG. 3 is a longitudinal sectional view taken at a vertical planeindicated in FIG. 2. by the arrows 3-3, as viewed in the direction ofthose arrows; the section view of FIG. 3 is substantially enlarged toshow details, but a large middle section has been removed as indicated,in order to reduce the length of the illustration;

FIG. 4 is a transverse section view, taken at a vertical plane, andviewed in the direction of the arrows indicated by the numerals 4-4 inFIG. 2;

FIGS. 5a and 5b are perspective views of the bridge structure sidewallsand the chord bar magazines, respectively, with their center sectionsremoved for purposes of compact illustration;

FIG. 6 is a fragmentary sectional detail view, looking down at ahorizontal plane indicated in FIG. 4 by the numerals 66, and showing theindexing mechanism for positioning the chord bar magazine at each of theseveral positions to which it may be shifted;

FIG. 3a is a corner detail of the chord zither, seen in perspective, inthe direction of the arrow 3a in FIG. 2, showing the preferred form ofmicrometer screwed turning;

FIG. 7a is a perspective view of a chord bar, illustrated with a chordbar operating button positioned on it;

FIG. 7b is a detail of a fragmentary corner of the chord bar magazine,seen in perspective, showing the vertical slots in which the ends of thechord bars are seated on helical springs, to provide a resilientmounting;

FIG. 8 is a plan view of the preferred form of wooden structure for theinterior of the sound box of the chord zither of the invention, shownwith the upper and lower panels removed, to reveal internalconstruction, but with the sound hole location indicated in dashedoutline; and

FIGS. 9 and 10 are two longitudinal sectional views of the sound boxconstruction of FIG. 8, seen at the vertical planes indicated by thearrows 99 and 10-10, respectively, in FIG. 8.

A preferred form of the chord zither of the invention is illustrated inFIGS. 1 and 2, in perspective and plan views, respectively, and isdesignated generally by the numeral 10.

The major parts of the chord zither 10 are a shallow wooden sound box11, approximately a right triangle in plan view; a triangular outerframe 12, preferably made of chrome plated steel tubing; a bridgestructure :13, preferably constructed with wooden sidewalls and analuminum plate prop, as will be described hereinafter; and a chord barmagazine, which is transversely slidable within the bridge structure 13.

The chord bar magazine 14 contains sixteen chord bars (one of which isactually a damper bar), these bars being identified generally by thenumeral 15 as seen, for example, in cross-section in FIG. 3.

The top part of the bridge structure 13 serves as a key table '16, whichis a rectangular aluminum plate about A; of an inch thick in theembodiment illustrated. Mounted in key table 16 are sixteen depressiblekeys, indicated generally by the numeral 17. The keys 17 oper ate thechord bars 15 as will be described hereinafter.

The strings of the chord zither -10 are designated generally by thenumeral 18, and are tuned at the left end of the zither 10 (as viewed inFIG. 2) by means of a micrometer screw tuning system indicated generallyby the numeral 19.

The strings 18, in the illustrated chord zither and in many other chordzithers, are 37 in number. They are tuned chromatically (i.e. athalf-tone intervals) which provide three full octaves on the instrument.The range extends from F below middle C to the F two octaves abovemiddle C.

The set of chord bars contains fifteen bars with spaced pieces of feltand openings on the undersides, as may be seen in FIG. 7a, allconstructed as well known in presently existing chord zithers. However,a sixteenth chord bar is provided with felt along its entire underside,to serve as a damper bar.

The shape of the preferred form of chord zither 10 is triangular, andparticularly a right triangle. Some previous zithers have also beentriangular, but most of them have had a trapezoidal form, because heavywooden plank-like parts were required to absorb string tension. In thepresent invention, substantially all the tension in the strings 18 istransmitted to the triangular tubular steel frame 12. Consequently, theframe shape 12 is dictated only by the requirements of the length ofstrings 18. In the design illustrated, the strings 18 are anchored tothe hypotenuse side 21 of the frame '12. At their opposite ends, wherethey are anchored by tuning system 19, the strings 18 pass over atransverse side member 22 of the frame 12. A longitudinal side member23, parallel to the strings 18, completes the triangle of frame 12.

In describing the chord zither 10, the three dimensions of the zitherwill be referred to as the string-axis dimension, parallel with sidemember 23, the transverse dimension, transverse to the strings 18 andparallel with side member 22; and the remaining dimension isconveniently designated and identified as sidewall height, being thevertical dimension of the zither sound box 11, best seen in thesectional views of FIGS. 3 and 4, in which the sound box vertical sidewalls are seen sectionally at 31, 32, 33 and 34.

The sectional views of FIGS. 3 and 4 may be compared With the plan viewof the sound box frame 30, with all other parts removed, seen in FIG. 8,and also the sectional views of the frame 30, seen in FIGS. 9 and 10.The principal parts of the sound box frame are seen to be a relativelymassive head block 31, and a smaller but also relatively massive footblock 32; and relatively thin long side walls 33 and 34.

The sound box frame 30 is covered by an upper panel 35 and a lower panel36, both being thin resilient panels of wood with acoustic propertiessuitable for musical instruments. Panels 35 and 36 correspond to thesimilar panels in a violin or other string instrument, and vibrate tosome degree along with the air contained within sound box cavity 37.Excessive vibration or movement of the panels 35 and 36 is prevented byinternal bracing 38 (seen in plan in FIG. 8), vertical support beingparticularly required in the vicinity of the sound hole 39; for example,see the vertical column 38a in FIG. 3 and FIG. 8, which supports oneside of sound hole 39, the hole location being indicated in FIG. 8 bythe phantom outline.

The sound box frame 30 is closely received within the tubular steelouter frame 12. Also, the sound box 11 is provided with great rigidityand strength by being anchored to the frame 12. In the particular chordzither illustrated in FIGS. 1 to 4, two methods of anchoring areprovided, although in a particular construction, either one alone wouldsuffice. One form of anchoring is by screws inserted from the interiorof sound box frame 30, passing completely through the frame and throughdrill holes in the inner surface of the outer frame 12. A set of suchanchoring screws is illustrated in the cross-sectional views of FIGS. 3and 4. Screw 40 passes through foot block 32 and drill hole 40a; screws41 and 42 pass 6 through side walls 33 and 34 and drill holes 33a and34a respectively.

However, the second method of anchoring is much preferred, and has beenfound adequate for anchoring outer frame 12 and sound box :11 inpermanent assembly with each other, Without the additional use of screwssuch as screws 40, 41 and 42. This preferred method of anchoring issimply to attach the outer frame 12 is assembled position by means ofbridges of a suitable plastic resin. A preferred material for thispurpose is one of the epoxy plastics, such as are used in theconstruction of boats. The epoxy resin is prepared by mixing it with ahardening catalyst; for a few minutes it may be tamped into place andtrimmed to a smooth surface; after that it will harden into a verystrong ridge of material bonded to both the wood of the sound box andthe steel surfaces of the outer frame 12. In the chord zither 10, it maybe seen from the cross-sectional FIGS. 3 and 4 that the plasticmaterial, as shown at 45, 46, 47 and 48 forms a pair of continuousbonding ridges one just above and one just below a horizontal planeindicated by the numeral 49 in FIG. 3, which is defined by theperipheral line of contact between sound box frame 30 and outer frame12.

In the preferred form illustrated, upper panel 35 projects horizontallyabout a quarter of an inch all the way around the periphery of sound boxframe 30, making substantially tangential contact with the top of thetubular metal outer frame 12.

Sound box frame 12 may be provided with an outer frame support step 50,seen in plan in FIG. 8, and in section in FIG. 3. In the particularconstruction illustrated, step 50 is a lower projecting shoulder portionof the head block 31, and supports only the transverse member 22 ofouter frame 12. However, it will be obvious that the step could beextended around the lower periphery of sound box frame 12 if furthersupport for outer frame 12 is found desirable for a particularconstruction.

The strings 18 are mounted on the chord zither 10 in a unique fashionbest illustrated in FIGS. 3 and 3a. Strings 18 are supported a fractionof an inch above upper panel 35 by means of fret ridges 51 and 52, whichmay be seen in plan view in FIG. 2. Strings 18 are preferably made of ahigh grade steel piano wire, suitable weighted for the lower notestrings. Consequently, although fret ridges 51 and 52 may be wood orplastic, it is desirable to protect their edges by means of transversesteel rods 51a and 52a.

As seen in the plan view of FIG. 2, and the cross-sectional view of FIG.3, each of the strings 18 has its foot end anchored to tubular frame 12.For example, in the chord zither 10, the foot end of each string 18passes through diametrically opposite bore holes 55 anl 56 in the outerframe 12, and is tied to a small tie-bar 57.

The tuning system 19 of chord zither 10 anchors the head end of thestrings .18. In the cross-sectional view of FIG. 3, and the detailperspective view of FIG. 3a, it is seen that the tuning system 19 iscomprised of a series of tuning screws 61, associated tuning nuts 62,and an anchor plate 63. In the plan view of FIG. 2, the edge of anchorplate 63 can be seen and also the outer edges of the 37 screws 61 andnut 62, a screw and nut set being provided for each of the 37 strings.

The cross-sectional view of FIG. 3 reveals that anchor plate 63 isscrewed by screws 64 to a recess 65 provided in foot block 31.

FIGS. 3 and 3a also show, as a preferred form of the invention, that thestrings 18 are laid over the upper and outer quadrant of the transversemember 22 of outer frame 12, so that each string is tuned by a verticalpull exerted by tuning screw 61. As tuning screw 61 is turned, fortightening, for example, the tuning nut 62 is pulled down, and a string18 attached to the nut by an anchoring knot 66 is tightened. Thedownwardly moving nut 62 slides over the outer surface of the step 50 ofhead block 31.

It will be seen that substantially all of the tension of strings 18 isabsorbed by outer frame 12. Some compressive forces are transmittedthrough fret ridges 51 and 52 and tuning plate 65 to the sound box frame30, but these do not require the massive construction found in the soundboxes of zithers heretofore known. Thus, the sound cavity 37, asillustrated in FIGS. 3 and 4, is many times larger than the soundcavities found in chord zithers and classical zithers of the past.

It will also be seen that the use of the outer frame 12 for mounting thestrings 18 has entirely eliminated the notoriously bad tuning problem ofzithers. Whereas zithers of the past have tended to go out of tuneovernight, the chord zither 10 has been found to stay in tune almostindefinitely, unless there are extreme swings in the temperature.

A typical chord bar 15, as used in the present invention, is illustratedin perspective in FIG. 7a. Chord bar 15 resembles the chord bars ofprior art, with this important difference: the key 17, used to operatethe chord bar 15, is not attached to the chord bar, in the preferredform of the invention. Instead, key 17 has an underside slot 70, intowhich chord bar 15 is slidably received. The upper part of key 17 is abutton 71 which projects upwardly through key openings 72 (seecross-sectional views FIG. 3 and FIG. 4) in key table 16.

The chord bar 15 is constructed of a bar member 75 and a series ofspaced felt pads 76. Bar member 75 may be wood, pressed compositionwood, plastic, or the like. Felt pads 76 are arranged to dampen certainstrings, but with spaces allowing others to vibrate, in a differentarrangement for each chord bar, to produce the chords desired. In thepresent invention, the chord bar 15 must have its felt pads 76 speciallydesigned, different from the chord bars of the prior art, so that thechord bar may produce different chords when shifted longitudinally ofthe chord bar (transversely over the strings 18).

In the preferred form of the present invention, the chord bars 15 arepermanently housed in the chord bar magazine 14, which may be seen inthe perspective view of FIG. B. The magazine 14 is substantially aninverted sheet metal box structure bridging the strings 18, and is seento be comprised principally of the chord bar housing 80, and right andleft pedestals 81 and 82, respectively. Right pedestal 81 is seen incross-section on the left side of FIG. 4 (because of the direction ofviewing) and left pedestal 82 is seen on the right side of FIG. 4.

The cross-sectional views of FIGS. 3 and 4 reveal that the chord barhousing portion 18 is entirely open underneath, as indicated at 83, topermit the downward movement into contact with the strings 18 of any ofthe chord bars 15. Also, the upper wall 84 of the chord bar housing 18has a large rectangular opening 85, exposing the upper edges of thechord bars 15 to contact with the corresponding keys 17, as illustratedin FIG. 7A.

Each of the sixteen chord bars 15 (15 true chord bars and one damperbar) is resiliently supported over the strings 18 by a pair of smallcoil springs, 88 and 89 as viewed in the cross-sectional view in FIG. 4.The fragmentary detail view of FIG. 7B reveals the internal constructionof left pedestal 82, right pedestal 81 being constructed in exactly thesame manner, except facing opposite. The interior space of pedestal 82serves as a chamber 90 for housing the springs 89, chamber 90 beingcompartmented by vertical partition 91 into individual compartments 92for each of the springs 89. The fragmentary perspective view of FIG. 7Band the transverse cross-sectional view of FIG. 4 reveal that each endof the bar member 75 of the chord bars 15 is vertically movable withinthe upper part of one of the spring compartments 92, being supported atright and left ends by springs 88 and 89, respectively.

The chord bar magazine 14 is housed in the bridge structure 13, which ispreferably constructed as illustrated of a key table 100 supported onsidewalls 101 and 102,

which latter are seen in perspective in FIG. 5A. A desirable form ofconstruction is to use a light but very strong aluminum plate for keytable 100, and a good quality of hardwood for sidewalls 101 and 102. Thebridge structure 13, when assembled, is anchored to sound box 11 bymeans of screws 103. It is important, in order to achieve substantialrigidity at construction, that the anchoring screws 103 be received intothe sound box 11 at points very near to outer frame 12.

In the preferred form of the invention illustrated, magazine 14 istransversely slidable, on its pedestals 81 and 82, within the bridgestructure 13, in order by its position, to provide the player with awide range of choices in chord bar operation. To provide for positivelocation of the chord bar magazine 14 in any of its several positions,an indexing mechanism 110, is illustrated in FIG. 6. This indexingmechanism is comprised of a spring detent ball 111, resiliently mountedin a recess 112 in the sidewall 101. The ball 111 snaps into position inany one of several indexing holes 113 in the side of chord bar housing80.

It will be noted in this connection, that the upper opening in the chordbar housing 80 has sufficient length, in the direction of chord bars 15,to permit operative contact between the keys 17 and the chord bar 15 forall the transverse positions of the magazine 14 within the bridgestructure 13. Although the cross-sectional view of FIG. 4, and thhorizontal sectional view of FIG. 6 show only six indexing holes 113,because of difficulty in illustrating a larger number, the usual numberof index positions, in corresponding holes 113, is twelve. Thus, withfifteen chord bars, and twelve indexing positions, 180 different chordsmay be played in a typical embodiment of the zither 10, as illustrated.

As seen in the'preferred construction, in FIG. 2, a larger key 17A isused over the chord bar 15A (see the longitudinal sectional view of FIG.3) which serves as a damper for all of the strings 18.

Also, the upper surface of key table is provided with identifying labelsadjacent each of the key openings 72 adjacent the upper ends 71 of eachof the keys 17.

As seen in FIG. SE, a chord identifying card 211 is attached to theupper surface of magazine 14. One line of card 211 can be read by theplayer through a window 212 provided in the key table 100. In this way,the player knows in which index position he has placed chord barmagazine 14 within the bridge structure 13.

An additional convenient teaching aid is a chord bar description card113 which is attached to the upper surface of key table 100, and hasprinted on it some explanatory material for each of the chord bars 15.

It will be seen from the foregoing, that the present invention, in itspreferred form, provides for transversely sliding magazine 14 withinbridge structure 13. It will be obvious that several different magazines14 might be employed, each having a distinctive set of chord bars 15.Also, it will be obvious that the invention could be simplified byeliminating the transverse sliding feature, while retaining chord barmagazine 14 independent of the bridge structure 13. Thus, one couldswitch chord bars by substituting magazines 14, even without thetransverse sliding feature of the preferred embodiment illustrated.

Many other variations, modifications, simplifications, and changes inthe invention might be made, Without departing from the scope of theinvention in its broadest and most general sense. It is my intention tocomprehend all such modifications within the boundaries of the followingclaims.

I claim:

1. A chord zither which includes:

an elongated, shallow sound box, made of acoustically resonant materialand having a relatively long string-axis dimension extending from a headend to foot end, a shorter transverse dimension, and a substantiallysmaller sidewall height normal to said string-axis and transversedimensions;

an outer frame of material substantially stronger and more rigid thansaid sound-box material, said outer frame closely enclosing said soundbox;

a set of strings corresponding to a predetermined series of musicalnotes disposed above said sound box and extending in said string-axisdimension, said strings being anchored to said outer frame at their endstoward said foot end and passing over said outer frame at said head end;

a tuning system comprised of a set of adjustable anchors,

one for each of said strings, said anchors being attached to said zitherat said head end to carry the tension of said strings between head andfoot ends of said outer frame;

a bridge structure disposed over said strings and based at each end nearsaid outer frame; and

a set of chord bars contained within said bridge structure, each of saidbars being individually manually movable into contact with said strings.

2. A chord zither as described in claim 1 in which:

said sound box is constructed with relatively massive head and footblocks at each end of said string-axis dimensions, sidewalls ofsubstantially lighter construction than said blocks, said sidewallsconnecting corresponding ends of said head and foot blocks to form asound box frame, an upper panel with fret ridges supporting said stringsand having a sound hole, a lower panel closing the opposite side of saidsound box frame, said panels being substantially less stiff than saidside walls, and internal bracing means for supporting of said panels;and said bridge structure is mounted on said head block with attachmentpoints near said outer frame.

3. A chord zither as described in claim 2, in which:

said head block is provided with an outwardly projecting step under thehead end of said outer frame, and each of said adjustable anchor-scomprises a vertically disposed screw anchored to said step below saidouter frame, and an anchor nut vertically movable on the outer surfaceof said step, by rotation of said screw, thereby applying tuning tensionto a zither string attached to said anchor nut.

4. A chord zither as described in claim 1, in which:

said chord bars are housed in a magazine, which is slidable within saidbridge structure transversely over said strings, and said bridgestructure has walls at at least one side of said zither defining anopening to permit the removal of said magazine with its contained set ofchord bars, and the substitution of another magazine containing adifferent set of chord bars.

5. A chord zither as described in claim 4, in which:

a set of buttons for individual opration of each of said chord bars ispermanently retained in the top portion of said bridge structure, saidbuttons being vertically movable in said bridge structure to depress acorresponding chord bar contained within said magazine within saidbridge structure, and said buttons having under surfaces permitting thetransverse sliding movement of said magazine to different positions ofsaid magazine over said strings, and to permit the removal of saidmagazine from said bridge structure.

6. A chord zither which includes:

a sound box constructed of a material equal in musical properties to thewood of stringed wooden instruments, said sound box having a relativelylong string axis dimension, a shorter transverse dimension, and asubstantially smaller sidewall height normal to said string-axis andtransverse dimensions, said sound box being constructed with relativelymassive head and foot blocks at each end of said string-axis dimension,sidewalls of substantially lighter construction than said blocks, saidsidewalls connecting corresponding ends of said head and foot blocks toform a sound box frame, an upper panel with fret ridges and a soundhole, a lower panel closing the opposite side of said sound box frame,said panels being substantially less stiff than said side walls, andinternal bracing means for support of said panels;

an outer frame, said outer frame comprising a closed peripheralstructure of rigid metal tubing closely enclosing said sound box andincluding anchoring means anchoring said outer frame to said sound box;

a set of strings corresponding to a predetermined series of musicalnotes disposed above said upper panel on said fret ridges and extendingin said string-axis dimension each of said strings being anchored tosaid outer frame at its end, and having its head block end wrapped overthe surface of said outer frame;

a tuning system comprised of an anchoring plate at said head block end,a set of screw adjustable anchors, one for each of said strings,individually anchoring the head block ends of said strings to saidanchoring plate;

a bridge structure disposed over said strings transversely thereof andsupported on said head block adjacent said tubular frame;

a chord bar magazine transversely movable over said strings within saidbridge structure; and

a set of chord bars disposed transversely of said strings within saidmagazine, and resilient support means for each support bar, each of saidchord bars being downwardly movable in said magazine against saidresilient support means, for selective manual application to saidstrings.

7. A chord zither as described in claim 6, which includes an index stopmechanism in said bridge structure, and

contacting said chord bar magazine, to provide positive location of saidchord bar magazine at a plurality of positions transversely of saidstrings, for providing different chord bar musical arrangements for eachof said chord bar magazine positions;

a table of musical information displayed on the top side of said chordbar magazine, one set of information for each of siad indexed magazinepositions; and

an information viewing window in the top of said bridge structure forpresenting to the view of the player, for each indexable position ofsaid chord bar magazine, the particular musical information relevant tosaid position.

8. A chord zither as described in claim 6, which includes:

a top wall in said chord bar magazine which is provided with an openingexposing the top sides of said chord bars over a substantial part oftheir length;

a set of chord bar operating keys, one for each of said chord bars,mounted in the top of said bridge structure, and vertically movabletherein, each of said keys being provided with a pair of downwardlydepending flanges closely received on opposite sides of a correspondingchord bar, to permit said chord bars to be shifted transversely of saidstrings, and to permit operation of said chord bars for all saidtransverse positions of said chord bar, by said keys.

9. A chord zither as described in claim 6-, in which:

said outer frame is positively located on, and anchored to the outerside walls of said sound box frame by laterally projecting wallstructure above and below said outer frame, closely receiving said outerframe and adhesively attached to it.

10. A chord zither as described in claim 6, in which:

said chord bar magazine includes right and left pedestals, disposed inparallel with the string axis dimension of said zither, at each side ofzither, and supporting the remaining structure of said magazine abovesaid set of strings, the bottoms of said right and left pedestals beingadapted to move slidably over the upper surface of said upper panel;

each of said pedestals includes internal wall structure defining a setof vertical slots, one for each of said chord bars, the opposite slotsin said right and left pedestals confining and guiding the correspondingchord bars in precise vertical movement; and in which a resilient coilspring is provided in each of said slots below each end of each of saidchord bars for resiliently urging the corresponding chord bar upwardly,within said magazine, to a. position retracted from contact with saidset of strings.

References Cited UNITED STATES PATENTS 12/1896 Dolge 5/ 1901 Stewart 2/1920 Cohn 4/ 1926 Hanson US. Cl. X.R.

